The invention relates to abrasive articles comprising or prepared from a nonwoven, binder, and abrasive particles. More specifically, the invention contemplates specific constructions of such abrasive articles that comprise a nonwoven, a layer having a binder and abrasive particles adhered or attached thereto, and another layer containing a binder and abrasive particles. The invention also relates to methods of making such nonwoven abrasive articles.
Abrasive articles are used industrially, commercially, and at a consumer level, to facilitate preparing other materials for use or processing. Exemplary uses of abrasive articles include treatment of a surface before priming or painting; cleaning a material to remove oxidation or debris; grinding or abrading a material for shaping; etc. In these applications, abrasive articles may be used to grind a surface or workpiece to a certain shape or form, to abrade a surface to clean or to facilitate bonding with a coating such as paint, or to provide a desired finish, especially a smooth finish.
Coated abrasive sheets of paper, cloth, and vulcanized fibers, and coated nonwoven materials, are examples of materials known to be useful in and as abrasive articles. These and other such materials can be formed into useful articles such as discs (which can sometimes be mounted onto a power tool), pads, sheets, wheels, sponges, and composites or combinations of these. The grinding or finishing properties of the abrasive article can be tailored to some degree to provide a desired level of aggressive removal of material, balanced with the need for a particular surface finish. These needs can also be balanced with the need for a relatively long useful life for the abrasive article. Typically, however, the useful life of an abrasive article is not suitably long, and therefore, there is a continuing need to provide new and improved abrasive articles that exhibit relatively longer useful lives, e.g., as compared to presently known and available abrasive products. It would be particularly desirable to identify such abrasive articles which also exhibit other advantageous properties, such as the ability to aggressively remove material, optionally balanced with an ability to provide a desirably smooth surface.
The present invention provides abrasive articles useful in surface conditioning operations and methods for the manufacture of such articles. The abrasive article can preferably have a useful combination of properties including long life, flexibility, and the ability (based in part on choices of materials used for its construction, e.g., abrasive particles, nonwoven, binders, etc.) to provide a desirably smooth finish balanced with desired aggressiveness in removing material.
In one aspect the invention provides a method for preparing an abrasive article. The method includes the following steps: applying a first binder precursor to a nonwoven; applying first abrasive particles to the first binder precursor; and applying a slurry to the first binder precursor and first abrasive particles, wherein the slurry comprises a second binder precursor and second abrasive particles, the second abrasive particles preferably having abrasive properties similar to those of the first abrasive particles. After application of the slurry, the first and second binder precursors can be exposed to conditions that will cause hardening of the first and second binder precursors. In a preferred embodiment of the method of the invention, during the time prior to application of the slurry, the applied first binder precursor is not exposed to conditions to cause hardening of the first binder precursor.
Another aspect of the invention relates to particularly preferred steps combined into an embodiment of the method. This preferred method includes the step of providing a nonwoven comprising fibers bonded to one another at their mutual contact points and having a first major surface, a second major surface, and a middle portion extending therebetween. A first binder precursor is applied to the nonwoven, preferably in an amount sufficient to provide a dry coating weight of about 200 grams per square meter or greater; the first binder precursor is preferably a phenolic, an aminoplast having pendant xcex1,xcex2-unsaturated carbonyl groups, a urethane, an epoxy, an ethylenically unsaturated material, an acrylated isocyanurate, a urea-formaldehyde, an isocyanurate, an acrylated urethane, an acrylated epoxy, a bismaleimide, an epoxy having fluorine substituent groups, or a combination of these. First abrasive particles are applied to the first binder precursor. A slurry is applied to the first binder precursor and first abrasive particles, preferably in an amount to provide a dry add-on weight of about 200 grams per square meter or greater; the slurry comprises second abrasive particles preferably having abrasive properties similar to those of the first abrasive particles and a second binder precursor that includes an acrylate, a phenolic, a polyurethane, a polyurea, a styrene-butadiene rubber, a nitrile rubber, a polyisoprene, or a combination thereof. After application of the slurry, the first and second binder precursors are exposed to conditions to cause hardening of the binder precursors.
In another aspect, the invention relates to abrasive articles constructed of materials including a nonwoven; a binder layer contacting the nonwoven and at least partially filling spaces between fibers of the nonwoven; first abrasive particles adhered to the binder layer; and a slurry layer comprising a second binder and second abrasive particles preferably having abrasive properties similar to those of the first abrasive particles, the slurry contacting the nonwoven and at least partially filling spaces within the fibers of the nonwoven. The article can be manufactured and processed into various forms such as a disc, a pad, a belt, a wheel, or a sheet, etc., or combinations or composites thereof.
As used herein, certain terms will be understood to have the meanings as set forth herein. xe2x80x9cFiberxe2x80x9d refers to a threadlike structure comprising any of the materials as described herein. The term xe2x80x9cprecursorxe2x80x9d refers to a material such as a prebond precursor, a binder precursor, a size coat precursor, etc., that can be coated onto a nonwoven and hardened, e.g., to bond the fibers at their mutual contact points, or to adhere particles. Upon hardening of the precursor, the hardened material is referred to using the same general designation (e.g., first or second binder, size coat, etc.), but without being referred to as a xe2x80x9cprecursorxe2x80x9d.